Link training scheme for displayport source repeaters

ABSTRACT

A system and a method for configuring communication between a source device and a sink device using captured configuration data are described. The source device communicates with a repeater, which modifies received data to facilitate transmission to the sink device, using a communication channel. The communication channel transmits video and/or audio data from the source device to the sink device. An auxiliary communication channel is used to communicate configuration data between the source device and sink device to optimize transmission and receipt of data through the communication channel. The repeater is coupled to the auxiliary communication channel and passively captures configuration data from the auxiliary communication channel. The repeater uses a subset of the captured configuration data (e.g., data rate, voltage swing, pre-emphasis, etc.) to modify how the repeater transmits data to the sink device using the communication channel.

BACKGROUND

1. Field of Art

The present invention generally relates to the field of integratedsemiconductor circuits, and more specifically, to high-speed integratedsemiconductor circuits for interfacing with digital video or audio.

2. Description of the Related Art

DisplayPort is an industrial standard of digital interface between twoor more devices. Commonly, a DisplayPort interface controls transfer ofvideo and/or audio from a source device, such as a computer, a digitalvideo disk (DVD) player or a digital video recorder (DVR), to a sinkdevice, such as a television, a home theater system or a computermonitor. DisplayPort uses two channels, a Main Link and an AuxiliaryChannel (AUX-CH) for communication between source device and sinkdevice. The Main Link serially transmits video, audio and othersecondary data at rates of 1.62 Gigabits per second (Gbps) or 2.7 Gbpswhile the AUX-CH carries management and device control data forestablishment or configuration of the Main Link at a rate of 1 Megabitper second (Mbps). Transmission of data through the AUX-CH is initiatedby the source device allowing the source device to modify Main Linkcharacteristics, although the sink device may prompt modification of theMain Link by sending an interrupt request (IRQ) to the source device viathe AUX-CH.

A common function for the AUX-CH is handshaking to train the Main Linkbetween source device and sink device. Depending on the distance betweenthe source device and the sink device, the source device and sink deviceuse different parameter sets to optimize data transmission through theMain Link. Link training allows the source device and sink device tonegotiate with each other to determine the optimal Main Link parametersettings for different transmission scenarios. For example, linktraining allows the source device and sink device to determine valuesfor lane counter, link rate, transmission main link voltage swing, mainlink pre-emphasis to optimize transmission. For example, when the sourcedevice and sink device connected by a short length of DisplayPort cable,a high bit rate is used with minimum voltage swing and no pre-emphasis.Alternatively, when the source device and sink device are connected by along length of DisplayPort cable, a low bit rate is used with highervoltage swing and pre-emphasis values.

In certain implementations, the source device and sink device arecoupled to a repeater device. The repeater device reconditions datatransmitted through the Main Link, allowing the Main Link to transmitvideo and/or audio data over greater distances without degradation.Commonly, the source repeater device is in close proximity to the sourcedevice, such as on the same printed circuit board as the source deviceor within the same housing as the source device. Close proximity of therepeater and source device results in use of the physical layer of theMain Link to transmit video and/or audio data from the source device tothe sink device. Hence, the repeater device reconditions video and/oraudio data to a remote sink device using the Main Link. However, thesource repeater device does not automatically adjust the Main Linkconfigurations responsive to the link training configuration and/ormaintenance that is transmitted through the AUX-CH. Therefore,positioning the repeater device close to the source device impairs theaccuracy of link training by the source device as the source devicebases configuration on the short distance between source device andrepeater device rather than the complete distance between source deviceand sink device.

SUMMARY

In an embodiment, a repeater comprises a listening module which iscoupled to an auxiliary communication channel which communicatesconfiguration data between a source device and a sink device. Thelistening module captures configuration data that is transmitted usingthe auxiliary communication channel. An interceptor is coupled to thelistening module and classifies configuration data captured by thelistening module. The interceptor allows generation of a subset of thecaptured configuration data having specific characteristics, such asdata associated with link training. A parameter setting module iscoupled to the interceptor and modifies a configuration setting of therepeater responsive to a subset of the captured configuration data. Thisallows the repeater to be configured responsive to data transmittedbetween the source device and the sink device so that the repeater andsource device are configured using the same configuration data. Thisbeneficially allows the repeater to more accurately replicates thecharacteristics of the source device.

In an embodiment, a communication channel is established between asource device and a repeater and used to communicate data. An auxiliarycommunication channel is also established between the source device andthe sink device and used to communicate configuration data. The repeaterthen captures configuration data from the auxiliary communicationchannel. In an embodiment, the repeater passively captures theconfiguration data from the auxiliary communication channel, allowingthe repeater to monitor the communicated data without disrupting theflow of data between source device and sink device. A characteristic ofthe repeater is then modified responsive to a subset of the capturedconfiguration data, allowing the configuration data to be used to modifyperformance of the repeater as well as the source device. This allowsthe repeater to approximate performance of the source device, whichimproves transmission of data using the communication channel.

The features and advantages described in the specification are not allinclusive and, in particular, many additional features and advantageswill be apparent to one of ordinary skill in the art in view of thedrawings, specification, and claims. Moreover, it should be noted thatthe language used in the specification has been principally selected forreadability and instructional purposes, and may not have been selectedto delineate or circumscribe the inventive subject matter.

BRIEF DESCRIPTION OF DRAWINGS

The disclosed embodiments have other advantages and features which willbe more readily apparent from the following detailed description and theappended claims, when taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a block diagram of a conventional data transmission system.

FIG. 2 is a block diagram of a system for transmitting video data andconfiguration data according to one embodiment of the invention.

FIG. 3 is a block diagram of a repeater for configuring communicationbetween a source device and a sink device according to one embodiment ofthe invention.

FIG. 4 is a flow chart of a method for passively capturing data from anauxiliary channel and configuring communication between a source deviceand a sink device according to one embodiment of the invention.

DETAILED DESCRIPTION

A system and method for configuring a communication channel including arepeater device coupled to a source device and a sink device aredescribed. For purposes of explanation, numerous specific details areset forth in order to provide a thorough understanding of the invention.It will be apparent, however, to one skilled in the art that theinvention can be practiced without these specific details. In otherinstances, structures and devices are shown in block diagram form toavoid obscuring the invention.

Reference will now be made in detail to several embodiments, examples ofwhich are illustrated in the accompanying Figures. It is noted thatwherever practicable similar or like reference numbers may be used inthe figures and may indicate similar or like functionality. The Figuresdepict embodiments of the present invention for purposes of illustrationonly. One skilled in the art will readily recognize from the followingdescription that alternative embodiments of the structures and methodsillustrated herein may be employed without departing from the principlesdescribed herein.

Some embodiments may be described using the expression “coupled” and“connected” along with their derivatives. It should be understood thatthese terms are not intended as synonyms for each other. For example,some embodiments may be described using the term “connected” to indicatethat two or more elements are in direct physical or electrical contactwith each other. In another example, some embodiments may be describedusing the term “coupled” to indicate that two or more elements are indirect physical or electrical contact. The term “coupled,” however, mayalso mean that two or more elements are not in direct contact with eachother, but yet still co-operate or interact with each other. Theembodiments are not limited in this context.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

In addition, use of the “a” or “an” are employed to describe elementsand components of the invention. This is done merely for convenience andto give a general sense of the invention. This description should beread to include one or at least one and the singular also includes theplural unless it is obvious that it is meant otherwise.

The algorithms and displays presented herein are not inherently relatedto any particular computer or other apparatus. Various general-purposesystems may be used with programs in accordance with the teachingsherein, or it may prove convenient to construct a more specializedapparatus to perform the required method steps. The required structurefor a variety of these systems will be apparent from the descriptionbelow. In addition, the present invention is not described withreference to any particular programming language. It will be appreciatedthat a variety of programming languages may be used to implement theteachings of the invention as described herein.

System Architecture

Referring now to FIG. 1, it illustrates one embodiment of a conventionalsystem 100 for communicating data between a source device 110 and a sinkdevice 130. In an embodiment, the conventional system 100 also includesa repeater 120 which is coupled to the source device 110 and the sinkdevice 130. The conventional system 100 includes two data transmissionchannels, an Auxiliary Channel (AUX-CH) 140 and a Main Link 150.

The source device 110 is any device which transmits video and/or audiodata, such as a digital video recorder (DVR), a digital video diskplayer (DVD) player, a computer, a hard drive or another storage deviceincluding video and/or audio data. In the conventional system 100, thesource device 110 is the master device and the sink device 130 is theslave device. Hence, the source device 110 initiates communication witha sink device 130 and also modifies characteristics of the Main Link 150communication channel between source device 110 and sink device 130.

In an embodiment, a repeater 120 is coupled to the source device 110 andthe sink device 130. For example, the repeater 120 receives input fromthe source device 110 via the Main Link 150 and then reconditions thereceived signal from the source device 110. The reconditioned signal isthen transmitted from the repeater 120 to the sink device 130 using theMain Link 150. Hence, the repeater 120 allows transmission ofhigh-quality video and/or audio data between the source device 110 andthe sink device 130, even when the source device 110 and the sink device130 are physically remote from each other.

The sink device 130 is any device which receives video and/or audiodata, such as a television (TV), computer monitor, home theater systemor other device which receives and processes video and/or audio data.Although the sink device 130 is the slave device, the sink device 130may also initiate Main Link 150 configuration. In an embodiment the sinkdevice 130 prompts initiation Main Link 150 configuration by sending aninterrupt request (IRQ) to the source device 110.

The AUX-CH 140 is a bi-directional communication link which transmitsdata for establishing or configuration the Main Link 150 between thesource device 110 and the sink device 130 or transmits data forcontrolling the source device 110 or sink device 130. For example, theAUX-CH 140 comprises an Alternating Current (AC) coupled, doublyterminated differential pair. In an embodiment, the AUX-CH 140 transmitsdata at a rate of 1 Megabit per second (Mbps). Additionally, the AUX-CH140 is used for the initial “handshake” establishing the Main Link 150between source device 110 and sink device 130. Further, the sourcedevice 110 uses the AUX-CH 140 to check the validity and status of theMain Link 150 and also uses the AUX-CH to implement any modifications tothe Main Link 150. Hence, the AUX-CH 140 is used to establish andmaintain the Main Link 150 connection between source device 110 and sinkdevice 130.

As the AUX-CH 140 communicates configuration and/or control data, theMain Link 150 transmits video and/or audio data from the source device110 to the sink device 130. The Main Link 150 is a uni-directionalcommunication channel which transmits video and/or audio data fromsource device 110 to sink device 130. For example, the Main Link 150comprises one or more AC-coupled, doubly-terminated differential pairs,commonly referred to as “lanes.” In an embodiment, the Main Link 150supports two data rates, 2.7 Gigabits per second (Gbps) and 1.62 Gbps.Hence, the Main Link 150 allows for high-speed transmission of videoand/or audio data from source device 110 to sink device 130 without linkor device configuration or maintenance data.

FIG. 2 shows a block diagram of a system 200 for transmitting video dataand configuration data according to one embodiment of the invention. Thesystem 200 includes a source device 110 and a sink device 130.Additionally, an AUX-CH 140 and a Main Link 150 are used to transmitconfiguration data and video and/or audio data, respectively. The sourcedevice 110, sink device 130, AUX-CH 140 and Main Link 150 are furtherdescribed above in conjunction with FIG. 1.

However, in system 200, the repeater 210 is coupled to both the AUX-CH140 and the Main Link 150. The repeater 210 receives input video and/oraudio data from the source device 110 via the Main Link 150 thenreconditions the received video and/or audio data. The reconditionedvideo and/or audio data is then transmitted from the repeater 210 to thesink device 130 using the Main Link 150. Additionally, the repeater 210receives data transmitted from the sink device 130 to the source device110 or from source device 110 to sink device 130 using the AUX-CH 140.Hence, the AUX-CH 140 is coupled to the source device 110 and the sinkdevice 130 and is also coupled to the repeater 210. This allows therepeater 210 to passively monitor data transmitted between the sourcedevice 110 and sink device 130 using the AUX-CH 140. As both the sourcedevice 110 and the repeater 210 are coupled to the AUX-CH 140, data fromthe AUX-CH 140 configures both the source device 110 and the repeater210, enabling the repeater 210 configuration to be similar to the sourcedevice 110 configuration.

In addition to monitoring data transmitted between the source device 110and sink device 130 using the AUX-CH 140, the receiver 210 alsointercepts a subset of the data transmitted via the AUX-CH 140. Forexample, the receiver 210 intercepts data or commands associated withlink training or similar configuration data or commands. The repeater210 then modifies one or more parameters of the repeater 210 to adjusthow video and/or audio data is transmitted via the Main Link 150. Thisallows modification of one or more repeater 210 parameters to optimizethe quality of the video and/or audio data received by the sink device130. The repeater 210 is further described below in conjunction withFIG. 3.

FIG. 3 is a block diagram of a repeater 210 for configuringcommunication between a source device 110 and a sink device 130according to one embodiment of the invention. The repeater 210 comprisesa receiver 300, an AUX-CH listening module 310, a training commandinterceptor 320, a parameter setting module 330 and a transmitter 340.However, in other embodiments, the repeater 210 includes differentand/or additional components than the ones shown in FIG. 3.

In one embodiment, a receiver 300 receives video and/or audio data fromthe Main Link 150. The receiver 300 is coupled to a transmitter 340,which receives the video and/or audio data from the receiver 300. Thetransmitter 300 then reconditions the video and/or audio data andtransmits the reconditioned video and/or audio data to a sink device130, or other device, using the Main Link 150. Additionally, therepeater 200 includes an AUX-CH listening module 310 which is coupled tothe AUX-CH 140 and to a training command interceptor 320. The AUX-CHlistening module 310 passively receives data transmitted via the AUX-CH140 and communicates the received data to the training commandinterceptor 320. The training command interceptor 320 is also coupled tothe parameter setting module 330 and communicates one or more commandsor data captured from the AUX-CH 140 to the parameter setting module330. The parameter setting module 330 is coupled to the transmitter 340and modifies one or more parameters associated with the transmitter 340responsive to the commands received from the training commandinterceptor 320.

The receiver 300 is coupled to the Main Link 150 and to the transmitter340. The receiver 300 receives video and/or audio data from the MainLink 150 as input and communicates the received data to the transmitter340. In various embodiments, the receiver 300 comprises any device whichreceives video and/or audio data.

The AUX-CH listening module 310 is coupled to the AUX-CH 140 andpassively monitors the AUX-CH 140. Additionally, the AUX-CH listeningmodule 310 is also coupled to the training command interceptor 320,allowing the AUX-CH listening module 310 to communicate data from theAUX-CH 140 to the training command interceptor 320. This allows theAUX-CH listening module 310 to non-intrusively monitor data transmittedvia the AUX-CH 140 and capture data transmitted using the AUX-CH 140without disrupting transmission of data between source device 110 andsink device 130 via the AUX-CH 140. In one embodiment, the AUX-CHlistening module 310 generates a copy of data transmitted through theAUX-CH 140 without altering or delaying transmission of data betweensource device 110 and sink device 130.

The training command interceptor 320 compares data received from theAUX-CH listening module 310 with stored information describing datatypes and/or commands to identify a subset of the transmitted data forfurther processing. For example, the training command interceptor 320compares data transmitted via the AUX-CH 140 to data describing linktraining commands and stores link training commands and not other typesof data transmitted via the AUX-CH 140. Hence, the training commandinterceptor 320 reduces the amount of captured data that is subsequentlyprocessed by the parameter setting module 330. This allowsidentification of the captured data most relevant to configuring one ormore transmitter 340 settings and discarding of captured data lessrelevant to transmitter 340 configuration. For example, the trainingcommand interceptor 320 identifies commands associated with linktraining and communicates those commands to the parameter setting module330 while discarding other commands.

The parameter setting module 330 is coupled to the training commandinterceptor 320 and to the transmitter 340. Data or commands captured bythe training command interceptor 320 are communicated to the parametersetting module 330 as input. Responsive to the received data orcommands, the parameter setting module 330 outputs parameter settings tothe transmitter 340 to modify one or more characteristics of thetransmitter 340. This allows the transmitter 340 to substantiallyreplicate the settings of the source device 110 by performing theconfiguration commands transmitted to the source device 110 at therepeater 200. Hence, the parameter setting module 330 adjusts one ormore transmitter 340 characteristics responsive to the captured data, sothat data from the AUX-CH 140 configures both the source device 110 andthe transmitter 340, which improves the quality of the video and/oraudio data transmitted by the repeater 200.

In various embodiments, the AUX-CH listening module 310, the trainingcommand interceptor 320 and the parameter setting module 330 compriseone or more processes executable by a hardware state machine, aprocessor (not shown) and/or one or more firmware applications. Theprocess or processes can be configured to operate on a general purposemicroprocessor or controller, a field programmable gate array (FPGA), anapplication specific integrated circuit (ASIC) or a combination thereof.In an embodiment, one or more of the AUX-CH listening module 310, thetraining command interceptor 320 and the parameter setting module 330comprise a processor configured to process data describing events whichmay comprise various computing architectures including a complexinstruction set computer (CISC) architecture, a reduced instruction setcomputer (RISC) architecture or an architecture implementing acombination of instruction sets. A single processor or multipleprocessors can be used to implement one or more of the AUX-CH listeningmodule 310, the training command interceptor 320 and the parametersetting module 330.

For purposes of illustration, FIG. 3 shows the AUX-CH listening module310, the training command interceptor 320 and the parameter settingmodule 330 as discrete modules. However, in various embodiments, any orall of the AUX-CH listening module 310, the training command interceptor320 and the parameter setting module 330 can be combined, allowing asingle module to perform the functions of one or more of theabove-described modules.

The transmitter 340 is coupled to the Main Link 150 and the receiver300. The transmitter 340 receives data from the receiver 300 thenreconditions or replicates the received data to facilitate communicationof the video and/or audio data. The transmitter 340 is also coupled tothe parameter setting module 330 which modifies data amplification, datareplication or other characteristics associated with the transmission ofvideo and/or audio data responsive to data from the AUX-CH 140. Thetransmitter then communicates the modified video and/or audio data to aremote device, such as the sink device 130, using the Main Link 150.

System Operation

FIG. 4 is a flow chart of a method 400 for passively capturing data froman auxiliary channel and configuring communication between a sourcedevice and a sink device according to one embodiment of the invention.Those of skill in the art will recognize that other embodiments canperform the steps of FIG. 4 in different orders or include differentand/or additional steps than the ones described herein.

Initially, the AUX-CH listening module 310 receives 410 a command, or apattern of commands indicating the start of communication between thesource device 110 and the sink device 130 via the AUX-CH 140. Forexample, the AUX-CH listening module 310 receives 410 an initializationmessage or initialization packet as input. After the command, or patternof commands, indicating the start of communication, one or more commandsare transmitted between the source device 110 and the sink device 130using the AUX-CH 140. The received commands are communicated from theAUX-CH listening module 310 to the training command interceptor 320included in the repeater 200. The training command interceptor 320 theninterprets 420 the AUX-CH commands as they are received, allowing thetraining command interceptor 320 to identify different command types orto identify the purpose of subsequent commands.

After interpreting 420 a received command, the training commandinterceptor 320 determines 430 whether the received command is wanted.This allows the training command interceptor 320 to identify a subset ofthe received commands for further processing while disregarding otherreceived commands. For example, the training command interceptorcompares one or more values of a received command with stored valuesidentifying a desired command. Examples of desired commands includecommands modifying data transfer rate, Main Link voltage swings, MainLink pre-emphasis or other commands associated with link training.Responsive to determining 430 that a command is not associated with thestored values identifying a desired command, the AUX-CH listening module310 and training command interceptor 320 enter an idle state awaitingtransmission of subsequent commands, such as a message or series ofmessages indicating that transmission has stopped.

However, responsive to determining 430 a received command is associatedwith a stored value identifying a desired command, the received commandis intercepted 440 by the training command interceptor 320. In oneembodiment, the training command interceptor 320 generates a replica ofthe desired command which is communicated to the parameter settingmodule 330. After receiving the replica of the desired command, theparameter setting module 330 extracts information from the replica ofthe desired command and uses the extracted information to identify oneor more parameter settings which are communicated to the transmitter340. The transmitter 340 then uses the received parameter settings tomodify one or more operational characteristics, allowing modification ofhow the transmitter 340 communicates data using the Main Link 150.Alternatively, the parameter setting module 330 executes the receivedcommand, causing one or more configuration operations to be performed onthe transmitter 340. This modifies the transmitter 340 responsive to thereceived AUX-CH 140 data, allowing the AUX-CH 140 data to configure boththe source device 110 and transmitter 340

Upon receiving 450 a command, or pattern of commands, indicating thetermination of communication between the source device 110 and the sinkdevice 130, the AUX-CH listening module 310, training commandinterceptor 320 and parameter setting module 330 enter an idle stateuntil data indicating the start of a new communication is received 410.This idle state reduces the power consumption of the AUX-CH listeningmodule 310, training command interceptor 320 and parameter settingmodule 330.

The foregoing description of the embodiments of the present inventionhas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the present invention tothe precise form disclosed. Many modifications and variations arepossible in light of the above teaching. It is intended that the scopeof the present invention be limited not by this detailed description,but rather by the claims of this application. As will be understood bythose familiar with the art, the present invention may be embodied inother specific forms without departing from the spirit or essentialcharacteristics thereof. Likewise, the particular naming and division ofthe modules, routines, features, attributes, methodologies and otheraspects are not mandatory or significant, and the mechanisms thatimplement the present invention or its features may have differentnames, divisions and/or formats. Furthermore, as will be apparent to oneof ordinary skill in the relevant art, the modules, routines, features,attributes, methodologies and other aspects of the present invention canbe implemented as software, hardware, firmware or any combination of thethree. Of course, wherever a component, an example of which is a module,of the present invention is implemented as software, the component canbe implemented as a standalone program, as part of a larger program, asa plurality of separate programs, as a statically or dynamically linkedlibrary, as a kernel loadable module, as a device driver, and/or inevery and any other way known now or in the future to those of ordinaryskill in the art of computer programming. Additionally, the presentinvention is in no way limited to implementation in any specificprogramming language, or for any specific operating system orenvironment. Accordingly, the disclosure of the present invention isintended to be illustrative, but not limiting, of the scope of thepresent invention, which is set forth in the following claims.

1. A system for configuring communication between a source device and asink device comprising: a main communication channel coupled to thesource device, the main communication channel communicating data fromthe source device; an auxiliary communication channel coupled to thesource device and the sink device, the auxiliary communication channelcommunicating configuration data from the source device; and a repeatercoupled to the main communication channel and the auxiliarycommunication channel, the repeater receiving data from the sourcedevice using the main channel and transmitting the received data fromthe source device to the sink device and the repeater capturingconfiguration data from the auxiliary communication channel.
 2. Thesystem of claim 1, wherein the repeater further modifies one or moreparameters responsive to a subset of the configuration data capturedfrom the auxiliary channel.
 3. The system of claim 2, wherein therepeater modifies transmission of received data from the source deviceto the sink device responsive to the subset of the configuration datacaptured from the auxiliary communication channel.
 4. The system ofclaim 2, wherein the subset of the configuration data captured from theauxiliary communication channel comprises link training data.
 5. Thesystem of claim 4, wherein the link training data comprises at least onefrom the group of data transfer rate, communication channel voltageswings and communication channel pre-emphasis.
 6. The system of claim 1,wherein the repeater passively captures configuration data from theauxiliary channel.
 7. An apparatus for communicating data between asource device and a sink device comprising: a listening module coupledto an auxiliary channel, the auxiliary channel communicatingconfiguration data between the source device and the sink device,wherein the listening module captures configuration data from theauxiliary communication channel; an interceptor coupled to the listeningmodule, the interceptor classifying the captured configuration data fromthe auxiliary communication channel; and a parameter setting modulecoupled to the interceptor, the parameter setting module modifying aconfiguration setting responsive to a subset of the capturedconfiguration data from the auxiliary communication channel.
 8. Theapparatus of claim 7, further comprising: a receiver coupled to acommunication channel, the receiver receiving data from the sourcedevice; and a transmitter coupled to the receiver and the parametersetting module, the transmitter transmitting data to the sink deviceusing the communication channel, wherein the parameter setting modulemodifies transmission of data from the transmitter to the sink deviceresponsive to the subset of the captured configuration data from theauxiliary communication channel.
 9. The apparatus of claim 7, whereinthe subset of the configuration data captured from the auxiliarycommunication channel comprises link training data.
 10. The apparatus ofclaim 9, wherein the link training data comprises at least one from thegroup of data transfer rate, communication channel voltage swings andcommunication channel pre-emphasis.
 11. The apparatus of claim 7,wherein the repeater passively captures configuration data from theauxiliary channel.
 12. A method for configuring data communicationbetween a source device and a sink device comprising: establishing acommunication channel between the source device and a repeater, thecommunication channel for communicating data; establishing an auxiliarycommunication channel between the source device and the sink device, theauxiliary communication channel communicating configuration data;capturing configuration data from the auxiliary communication channelusing the repeater; and responsive to a subset of captured configurationdata from the auxiliary communication channel, modifying acharacteristic of the repeater.